This invention generally relates to balloon catheters, particularly balloon catheters for deploying stents, such as after percutaneous transluminal coronary angioplasty (PCTA) procedures.
In a typical PTCA procedure a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient's coronary anatomy where the balloon of the dilatation catheter is properly positioned within a stenosis to be dilated. The balloon is inflated with radiopaque liquid at relatively high pressures (generally greater than 4 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. The catheter may then be withdrawn from the stenosis or advanced further into the patient's coronary anatomy to dilate additional stenoses.
Very frequently the PTCA treatment modality includes the placement of a stent either simultaneously during the angioplasty or after a dilatation of a stenotic arterial region has been completed to provide long term lumen patency. Balloon catheters similar to those described above for dilatation are used to deploy stents within a patient's body lumen. Typically, an expandable stent is first disposed about the exterior of the deflated balloon on the distal extremity of the catheter in a constricted or otherwise unexpanded condition and then the catheter is advanced within the patient's body lumen until the stent mounted on the exterior of the balloon is at the location in which the stent is to be deployed, e.g. at the stenotic site of a previous dilatation. The balloon is inflated so as to expand the constricted or otherwise unexpanded stent against the wall defining the body lumen and then the balloon is deflated and the catheter withdrawn from the patient's body lumen. The expanded stent remains at the lumen site in an expanded condition when the catheter is removed.
Advances in material development for relatively non-compliant balloons designed for both dilatation and stent deployment have increased the tensile strength of the balloons allowing thinner balloon walls and thus lower catheter profiles. However, to obtain the benefits of a lower catheter profile, the wings which form when such balloons are deflated are wrapped around the inner member which extends through the interior of the balloon. The wrapped balloon may be covered with a protective sheath at least for handling and storage. Frequently, for stent delivery balloons, the stent is crimped onto a protective sheath covering which is somewhat elastically expansive so as to provide a more uniform expansion of the stent mounted on the sheath. The wrapped wings of the balloon are usually heat set in this condition so that the wings have a memory of the small wrapped dimensions when the balloon is deflated after inflation, e.g. for prepping, dilatation or stent deployment.
While some improvement in balloon profile has been obtained with the prior wrapped balloons, the procedures for forming the balloon with the desired memory complicates the manufacturing procedure and the use of the balloon. What has been needed is a catheter structure which simplifies the wrapping and eliminates the folding of the balloon wings and the heat setting thereof. The present invention satisfies these and other needs.